1、jdk动态代理代码实现

1、接口

java">public interface IUserService {

    void save();

   void delete();

}

2、接口实现

java">@Service
public class UserServiceImpl implements IUserService {

    @Override
    public void save() {
        System.out.println("UserServiceImpl.save");
    }

    @Override
    public void delete() {
        System.out.println("UserServiceImpl.delete");
    }
}

3、代理类创建

java">@Test
public void testJdkProxy(){

    //使用jdk动态代理生成 代理对象
    IUserService userServiceProxy = (IUserService) Proxy.newProxyInstance(
        this.getClass().getClassLoader(),   //类加载器
        userService.getClass().getInterfaces(), //给接口proxy 才可以生产代理
        new InvocationHandler() {  //代理对象执行的接口
            //代理对象 反射执行的方法
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

                //这里进行增强
                System.out.println("log 日志输出" + method.getName());

                //真实对象执行 delete、save的方法
                Object obj = method.invoke(userService,args);

                return obj;
            }
        }
    );

    System.out.println("userServiceProxy = " + userServiceProxy);
    userServiceProxy.save();
    userServiceProxy.delete();
}

4、原理

1、使用工具类生产代理对象 字节码

java">public class ProxyUtils{
	
	public static void main(String[] args) throws Exception {
        saveProxyFile();
    }
	
	private static void saveProxyFile() throws IOException {

        IUserService userService = new UserServiceImpl();

        FileOutputStream out = null;
        File file = new File("C:\\test\\" + "$Proxy0.class");
        file.createNewFile();
        try {
            byte[] classFile = ProxyGenerator.generateProxyClass(
			"$Proxy0",
                    userService.getClass().getInterfaces());
            out = new FileOutputStream(file);
            out.write(classFile);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.flush();
                    out.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2、源码分析